(1) Preheat the oven to 425 degrees Fahrenheit. If using cast iron, place the baking sheet into the oven to preheat.
(2) Put the stick of butter in the freezer for a few minutes. The colder it is, the better it will hold together during mixing and give the biscuits their "biscuit" texture.
(3) Mix together the flour, starter, baking powder, and salt. Make sure the starter is well incorporated into all of the dry ingredients.
(4) Cut the butter into the flour and starter mix. The fastest way is to grate it with a cheese grater - which works especially well when the butter is cold. But you can also cut it in with butter knives.
(5) Once the butter is fully incorporated, add the milk until the mixture comes together with a dough-like texture. The amount of milk may vary depending on how wet your sourdough starter is.
(6) Divide the dough into roughly 12 portions and lightly shape it into round disks. Place on the preheated baking sheet. They do not need to touch, but it will not hurt them if they do.
(7) Bake for ~17 minutes, until golden brown on top.
(8) These biscuits are best enjoyed warm! If you need them for a future meal, the dough freezes well.
Then, earlier this year, I made my own gluten free sourdough starter. Suddenly I needed a use for all the sourdough discard! Enter the Sourdough Biscuit. They have a tangy flavor from the sourdough, and a texture that is almost exactly like a proper biscuit. I use Bob's Red Mill All Purpose Baking Flour, which is a mix of chickpea flour, starch, sorghum flour, and fava bean flour. I love that this mix has some protein from the chickpea and fava bean flours, and no xanthum gum. It makes for a hearty guilt-free biscuit.
Please note, I bake my biscuits on my cast iron baking sheet. This toasts the bottom very nicely, and they slide right off the pan. I always put the pan in the oven to preheat. If you are not using a cast iron sheet, you may need to adjust the cooking time.